There are conventional techniques in which a trapezoidal shape having a small width on the reading side is formed by giving a bevel angle to the air bearing surface shape of a main magnetic pole layer by taking account of a case in which a skew angle is produced in a recording head. Since, however, none of these techniques use any spin torque oscillator (STO), it is difficult to achieve a recording density of 1 Tbpsi or more.
Also, when an STO layer and the main magnetic pole layer are processed by using the same mask in order to form the STO of the magnetic recording head on the main magnetic pole, the STO and main magnetic pole are processed by the same angle. This makes it difficult to give a bevel angle to only the main magnetic pole. When processing the STO layer and main magnetic pole layer by the same angle, it is possible to give a bevel angle to the STO and main magnetic pole, or give no bevel angle to the STO and main magnetic pole. For example, when the STO had a bevel angle, the size of an oscillation layer became larger than that of a spin injection layer forming the STO, and the oscillation driving current density increased. To implement a high-frequency magnetic field assisted recording head, it is important to design and form an STO capable of stably oscillating with a low driving current. A maximum current density that can be supplied to the STO is 2×108 A/cm2 when, e.g., the STO size is about 70 nm. If the current density is higher than that, the characteristics deteriorate due to, e.g., the heat generation and migration of the spin torque oscillator. On the other hand, when neither the STO nor the main magnetic pole has a bevel angle, data on an adjacent track is erased if a skew angle is produced in the magnetic recording head. Also, when the element size decreases as the density increases, magnetization directions in the element are readily matched, and this facilitates generating high-frequency oscillation. On the other hand, the element size approaches the mean free path of electrons, and this poses the problem of the scaling rule by which spin torque transfer in the STO is suppressed and the magnetic resistance change ratio decreases. There is a method by which the specular reflection effect is increased by forming an oxide or the like having magnetization on the sidewalls of the element, thereby relaxing the problem of the scaling rule caused by the mean free path of electrons. However, if an oxide or the like having magnetization is formed on the sidewalls of the oscillation layer of the STO, high-frequency oscillation from the oscillation layer is suppressed.